1. Field of the Invention
The present invention relates to a prevention against shifting of a tip seal mounted on a scroll compressor.
2. Description of the Prior Art
A prior art given in FIG. 10 to FIG. 12 is known as common in this kind of apparatus.
In the drawings, 1 denotes a stationary scroll, 1a denotes an end plate of the stationary scroll 1, 1b denotes a lap formed vertically and swirlingly on an inside 1c of the end plate 1a, 2 denotes a swirl scroll provided opposite to the stationary scroll 1, 2a denotes an end plate of the swirl scroll 2, 2b denotes a lap formed vertically and swirlingly on an inside 2c of the end plate 2a, and an arrangement is such that the scrolls 1, 2 are paired to face each other, the laps 1b and 2b are then engaged with each other, the stationary scroll 1 is fixed on a frame 3, and the swirl scroll 2 is swirled on an eccentric part 4a of a crankshaft 4 or a driving shaft. A reference numeral 5 denotes a needle bearing, the crankshaft 4 is supported on bearings 6, 7 fixed on the frame 3, 8 denotes a balance weight mounted on the crankshaft 4, 9 denotes a suction port of air or a gas to compress which is provided on the stationary scroll 1, and 10 denotes a discharge port of a compressed air. A reference numeral 11 denotes a tip seal, which is made, for example, of an elastic material having a self-lubricating efficiency and formed swirlingly. A reference numeral 12 denotes a nose portion of the tip seal 11, 13 denotes a spiral tip seal groove provided on the nose portion 12 longitudinally of the laps 1b, 2b, and the tip seal 11 is fitted in the tip seal groove 13. A reference character 13a denotes a bottom portion of the groove 13.
A reference numeral 15 denotes an oil feed port for feeding oil to the bearings for lubrication and cooling. The frame 3 is mounted in such manner as will cover the scrolls 1, 2 so as not to allow a lubricting oil fed from the oil feed port 15 to leak externally.
In consideration of an elongation due to thermal expansion, the tip seal 11 is shortened by l from the length of the tip seal groove 13. A reference character 11a denotes a discharge port side end portion of the tip seal 11, and 11b denotes a suction port side end portion of the tip seal 11.
In the above-described construction, a gas pocket P working as a compression chamber is formed between the the laps 1b, 2b mated to face each other and the end plates 1a, 2a by facing the stationary scroll 1 and the swirl scroll 2 provided projectingly from the end plates 1a, 2a respectively each other, the air is sucked in from the suction port 9 by moving the swirl scroll 2 round a central axis of the stationary scroll 1, and a compressed air is discharged into the gas pocket P (FIG. 3) formed according as the swirl scroll 2 is moved as above from the discharge port 10.
In the tip seal of a prior art scroll compressor, the construction is such that the tip seal 11 is fitted in the nose portion 12 of the laps 1b, 2b of the stationary scroll 1 and the swirl scroll 2, and both the scrolls 1, 2 are kept facing each other, then the nose portion 12 of the tip seal 11 is pressed onto the insides 1c, 2c of the end plates 1a, 2a of both the scrolls 1, 2, thereby preventing leakage from the nose portion 12 of the laps 1b, 2b.
However, in the prior art scroll compressor, since the tip seal 11 is kept shorter in length than the tip seal groove 13 in consideration of an elongation due to temperature rise arising according to an operation of the compressor, the tip seal 11 contracts due to a temperature drop or a discharge pressure applied on a discharge side end portion of the tip seal 11 and moves from the side of discharge port 10 to the side of suction port 9 along the tip seal groove 13, thus leaving a suction side end portion of the tip seal crushed. Thus, the tip seal will never revert from the contraction despite an actuation of the compressor to temperature rise. Consequently, the tip seal is not present on the side of discharge port 10, and a sealing between the gas pocket on a high pressure side and the gas pocket on a low pressure side cannot be realized at a nose of the laps 1a, 1b.